Significance of one and two carbon photoproducts in the photolysis of marine dissolved organic matter

海洋溶解有机碳（DOC）是地球上主要的碳库之一，但尽管多年的研究，DOC的生产和去除的途径和速率受到很大的限制。重要的是要确定海洋中的主要途径和速率，以更好地预测DOC循环在未来将如何变化，以及这些变化将如何改变全球碳循环。影响海洋DOC的一个潜在的重要过程是光化学，即有机分子在阳光下的分解。本项目将研究DOC的光化学破坏。这项工作的发现将引起生物学家、化学家、生态学家、气候科学家和海洋大气建模者的兴趣。该项目将为一名博士后学者、一名研究生和几名本科生提供研究和教育机会。该项目小组将通过一个项目网站、视频会议、在线论坛和互动博客与纽约州立大学、环境科学与林业学院的路易斯·斯托克斯少数民族参与计划联盟和当地美国化学学会为经济困难的高中生开展的SEED项目合作，参与公共宣传和教育。研究计划是重新评估两个长期存在的假设：溶解的无机碳（即，海洋溶解有机碳（DOC）的光化学分解产生的主要产物是二氧化碳，阳光驱动的化学作用是海洋DOC去除的一个重要过程。该项目将调查三个相互关联的问题：（1）是沿海到近海断面的丙酮，丙酮酸和C1-和C2-碳光产物的生产率的非线性函数的CDOM吸收，观察DIC？(2)DIC是DOC在开阔海域光解产生的主要碳光产物吗？(3)C1-和C2-碳光产物的产生，以及丙酮和丙酮酸盐，共同是每年海洋DOC的重要去除机制吗？为了解决这些问题，该项目将结合联合收割机实验室实验和为期19天的研究巡航。该项目将重点关注低分子量碳化合物，因为这些是DOC光解产生的主要产物，但还没有人共同测量这些化合物在海水中的光化学产生率。要考虑的化合物包括一氧化碳、溶解的无机碳、甲醛、乙醛、丙酮、乙二醛、乙醛酸盐、丙酮酸盐、甲酸盐和乙酸盐。该团队将测量光化学生产率，并确定这些化合物生产的波长和温度依赖的表观量子产率（AQY）。利用AQY数据，他们将利用遥感海洋颜色模拟深度分辨的光化学碳通量，以确定这一过程对海洋DOC循环的影响。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Marine dissolved organic carbon (DOC) is one of Earth’s major carbon reservoirs, but despite many years of study, the pathways and rates of DOC production and removal are poorly constrained. It is important to identify major pathways and determine rates in the oceans to better predict how DOC cycling will change in the future, and how these changes will alter the global carbon cycle. One potentially important process that affects marine DOC is photochemistry, the breakdown of organic molecules by sunlight. This project will investigate photochemical destruction of DOC. Findings from the work will be of interest to biologists, chemists, ecologists, climate scientists, and ocean-atmosphere modelers. The project will foster research and educational opportunities for one postdoctoral scholar, a graduate student, and several undergraduates. The project team will engage in public outreach and education through a project website, videoconferencing, online discussion forums, and an interactive blog in partnership with the State University of New York, College of Environmental Science and Forestry’s Louis Stokes Alliance of Minority Participation Program and the local American Chemical Society’s Project SEED for economically-disadvantaged high school students. The research plan is to re-evaluate two long-held assumptions: that dissolved inorganic carbon (i.e., carbon dioxide) is the main product produced from the photochemical breakdown of marine DOC, and that sunlight-driven chemistry is an important process in the removal of DOC from the oceans. The project will investigate three interrelated questions: (1) Are coastal-to-offshore transects in production rates of acetone, pyruvate and C1- and C2-carbon photoproducts nonlinear functions of CDOM absorption, as observed for DIC? (2) Is DIC the main carbon photoproduct produced from the photolysis of DOC in the open ocean? (3) Is the production of C1- and C2-carbon photoproducts, together with acetone and pyruvate, collectively a significant removal mechanism for DOC in the oceans on an annual basis? To address these questions, the project will combine laboratory experiments and a 19-day research cruise. The project will focus on low molecular weight carbon compounds because these are the main products produced from the photolysis of DOC, and yet no one has co-measured photochemical production rates of these compounds in seawater. Compounds to be considered include carbon monoxide, dissolved inorganic carbon, formaldehyde, acetaldehyde, acetone, glyoxal, glyoxylate, pyruvate, formate, and acetate. The team will measure photochemical production rates and determine wavelength- and temperature-dependent apparent quantum yields (AQY) for the production of these compounds. Using AQY data, they will model depth-resolved photochemical carbon fluxes using remotely sensed ocean color to determine the impact of this process in the marine DOC cycle.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.